Catalytic reformer with upstream and downstream supports, and method of assembling same

ABSTRACT

Engineers have attempted to reduce undesirable emissions from internal combustion engines by using apparatuses, such as catalytic reformers that include pre-combustion catalysts. An apparatus of the present invention includes an apparatus housing that defines at least a first flow inlet and includes an upstream support and a downstream support. The upstream support defines a plurality of second flow inlets, and the downstream support defines a first portion and a second portion of a plurality of outlets. A plurality of second flow paths are defined by a plurality of tubes extending between the plurality of second flow inlets and the second portion of the plurality of outlets. At least one first flow path is defined by a plurality of surfaces and fluidly connects the first flow inlet with the first portion of the plurality of outlets. At least one surface of the plurality of surfaces is coated with a pre-combustion catalyst. The downstream support preferably includes a plate with a predetermined porosity.

TECHNICAL FIELD

The present invention relates generally to catalytic reformers, and morespecifically to catalytic reformers for gas turbine engines that includea downstream support.

BACKGROUND

Engineers are constantly seeking strategies of reducing undesirablecombustion emissions, such as nitrogen oxides (NO_(x)). For instance,stringent government regulations limiting the amount of NO_(x) that canbe emitted from gas turbine engines has driven the industry to producegas turbine engines with NO_(x) emissions levels below 3 ppm. Over theyears, engineers have found that the lower the ignition temperature ofcombustion, the less NO_(x) the combustion will produce. Thus, in orderto achieve lower emissions levels, pre-combustion catalytic reformersthat reduce the ignition temperatures required for complete combustionof a fuel-air mixture are being used within gas turbine engines.

In a gas turbine engine, the catalytic reformer is generally positionedwithin a combustor assembly and downstream from a compressor assembly.The compressor assembly compresses ambient air, and delivers a portionof the compressed air to the combustor assembly to be mixed with fuel.Within the catalytic reformer, the fuel-air mixture passes over tubeswithin a tube bundle that are coated with a catalyst. The fuel-airmixture reacts with the catalyst creating radicals which aid instabilizing the flame downstream within the combustor assembly.

However, because many catalysts will not react with the fuel-air mixtureat the temperature of the compressed air leaving the compressorassembly, a fuel rich mixture is often needed to react with thecatalyst. Thus, not all of the compressed air leaving the compressorassembly will be mixed with the fuel. A portion of the compressed airthat is not mixed with the fuel can flow through each tube within thetube bundle of the catalytic reformer in order to absorb the heat fromthe tube bundles caused by the catalytic reaction.

Once the fuel-air mixture passes along the outer surfaces of the tubesand the compressed air passes within the tubes, the catalyzed fuel-airmixture and the compressed air are mixed together in a mixing chamberbefore being delivered to a combustor chamber. By mixing the fuel withall the compressed air prior to combustion, the risk of hot spots withinthe combustion chamber is reduced and a relatively uniform temperaturecan be maintained during combustion, leading to reduced NO_(x)production.

Although the catalytic reformers have succeeded in reducing NO_(x)emissions, the catalytic reformers are subjected to hostile environmentswithin the gas turbine engines. For instance, high temperatures can becreated by the reaction between the catalyst and the fuel, pre-ignitionwithin the catalytic reformer, and/or flashback ignition from thedownstream combustion. Vibrations can be caused by the flow of thecooling air inside the tubes, flow of the fuel-air mixture passing overthe tubes, and other system vibrations within the engine. Moreover,oxidation can cause corrosion within the catalytic reformer. Eventually,the stress of the high temperatures, the vibrations and/or corrosion maycause one of the tubes within the tube bundle to fail and break away.The tube may be forced downstream into a turbine assembly and severelydamage the engine.

In order to support and secure the tubes within the catalytic reformer,the catalytic combustor cooling tube vibration dampening devicedescribed in U.S. Patent Application No. US 2003/0056511 A1, by Bruck etal. on Mar. 27, 2003, includes regions on each tube within the bundlethat maintains tube to tube contact to supposedly better resistvibrations. Thus, rather than the tubes impacting one another duringvarious modes of vibration, the tubes rigidly support one another at thecontacting regions.

Although the tube to tube contact within the tube bundle of the Bruckcatalytic combustor may dampen the vibrations on the tube bundle, thetube to tube contact reduces the outer surface area of the tubes thatcan be coated with the catalyst. Thus, there is less surface area forthe catalyst to react with the fuel-air mixture, thereby reducing thefuel-air mixture's ability to stabilize of the downstream flame duringcombustion. Further, the costs of manufacturing and installing the tubeswith the contacting portions may be relatively high.

The present invention is directed at overcoming one or more of theproblems set forth above.

SUMMARY OF THE INVENTION

In one aspect of the present invention, an apparatus includes anapparatus housing that defines at least one first flow inlet andincludes an upstream support and a downstream support. The upstreamsupport defines a plurality of second flow inlets, and the downstreamsupport defines a plurality of outlets that includes a first portion anda second portion. At least one first flow path is defined by a pluralityof surfaces, and fluidly connects the first flow inlet to the firstportion of the plurality of outlets. At least one of the plurality ofsurfaces is coated with a pre-combustion catalyst. A plurality of secondflow paths is defined by a plurality of tubes that extend between theplurality of second flow inlets and the second portion of the pluralityof outlets.

In another aspect of the present invention, an apparatus includes meansfor securing a plurality of tubes that extend between an upstreamsupport and a downstream support within an apparatus housing. Theapparatus also includes means for introducing a fuel-air mixture flowoutside the plurality of tubes and a means for introducing an air flowwithin the plurality of tubes. The fuel-air mixture flow is introducedvia at least one first flow inlet defined by the apparatus housing, andthe air flow is introduced via a plurality of second flow inlets definedby the upstream support. There are means for contacting the fuel-airmixture flow with a pre-combustion catalyst, and means for deliveringthe air flow and the fuel-air mixture flow to a mixing chamber via aplurality of outlets defined by the downstream support.

In yet another aspect of the present invention, a method of assemblingan apparatus includes a step of forming at least one first flow path anda plurality of second flow paths through an apparatus housing. A firstend of a plurality of tubes is attached to a plurality of second flowinlets defined by an upstream support, and a second end of the pluralityof tubes is attached to a portion of a plurality of outlets defined by adownstream support. At least one surface of the first flow path iscoated with a pre-combustion catalyst.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a gas turbine engine, accordingto the present invention; and

FIG. 2 is a schematic representation of a catalytic reformer apparatuswithin the gas turbine engine of FIG. 1.

DETAILED DESCRIPTION

Referring to FIG. 1, there is shown a schematic representation of a gasturbine engine 10, according to the present invention. Although thepresent invention is illustrated within the gas turbine engine 10, itshould be appreciated that the present invention could apply within anyinternal combustion engine. The gas turbine engine 10 includes an enginehousing 11 that includes an outer casing 14. A combustor assembly 17includes an assembly housing 15 that is attached to the outer casing 14.The combustor assembly 17 is positioned downstream from a compressorassembly (not shown) and upstream from a turbine assembly (not shown).The compressor assembly is typically mechanically coupled to the turbineassembly via a central shaft. The compressor assembly draws ambient airinto the gas turbine engine 10 and compresses the air. The compressedair is delivered to a compressed air plenum 18 within the combustorassembly 17. The compressed air plenum 18 is defined by the assemblyhousing 15 and the outer casing 14 that preferably surrounds thecombustor assembly 17. The combustor assembly 17 includes an apparatus,herein referred to as a catalytic reformer 16 that is in fluidcommunication with a combustor 13. Although the present inventionillustrates only one combustor assembly 17, it should be appreciatedthat there could be any number of combustor assemblies within the casing14 disposed circumferentially about the central shaft operablyconnecting the turbine assembly and the compressor assembly.

The catalytic reformer 16 is in fluid communication with the compressedair plenum 18 via a plurality of compressed air inlets 21 andpre-combustion mixing regions 25. The catalytic reformer 16 is also influid communication with a fuel supply system that includes fuelinjectors 22 that inject fuel into the pre-combustion mixing regions 25.Within the catalytic reformer 16, a first portion of the compressed airenters the pre-combustion mixing regions 25 and mixes with fuel injectedby the fuel injectors 22 to create a rich fuel-air mixture. The richfuel-air mixture reacts with a pre-combustion catalyst 41 (shown in FIG.2) coated on an outer surface of a plurality of tubes 36 included withinthe catalytic reformer 16. In order to cool the catalytic reformer 16, asecond portion of the compressed air enters the catalytic reformer 16via the plurality of compressed air inlets 21 and is delivered throughthe plurality of tubes 36 included within the catalytic reformer 16.Although not necessary, a third portion of the compressed air ispreferably delivered through the combustor assembly 17 via a pilot flowpath 12 defined by a center body 19 of the combustor assembly 17. Thepilot flow path 12 is in fluid communication with and the compressed airflow plenum 18 via an air inlet 20 and the fuel supply system. Thecompressed air is swirled with fuel via an axial swirler 23 in the pilotflow path 12. The angular momentum of the swirl causes a vortex flowwith a low-pressure region 24 along a centerline of the pilot flow path12. Hot combustion products from the combustor 13 are continuouslyre-circulated upstream along the low-pressure region 24 and continuouslyignite the incoming lean fuel air mixture to create a stabile pilotfame. Those skilled in the art will appreciate that the approximately10-20% of the compressed air that enters the reformer 16 mixes with thefuel in the pre-combustion mixing regions 25, approximately 75-85% ofthe compressed air flows through the plurality of cooling tubes 36, andapproximately 5-10% of the compressed air flows through the pilot flowpath 12.

The combustor assembly housing 15 defines a mixing chamber 32 downstreamfrom the catalytic reformer 16 and upstream from the combustor 13. Thecatalytic reformer 16 is in fluid communication with the mixing chamber32 via a plurality of outlets 31. After passing through the catalyticreformer 16, the rich fuel-air mixture and the compressed air will mixwithin the mixing chamber 32 to form a lean fuel-air mixture. The leanfuel-air mixture is delivered to a combustor 13 in which it is ignitedto create a working gas. The working gas is delivered to the turbineassembly in which it is expanded through a series of rotatable bladesthat are attached to the shaft and stationary vanes. The blades andshaft rotate creating a mechanical force.

Referring to FIG. 2, there is shown a schematic representation of thecatalytic reformer 16 included within the gas turbine engine 10 ofFIG. 1. The catalytic reformer 16 includes a reformer housing 33 thatincludes an upstream support 34 that defines the plurality of secondflow inlets, herein referred to as the plurality of compressed airinlets 21, and a downstream support 30 that defines the plurality ofoutlets 31. The plurality of outlets 31 includes a first portion thatserve as the fuel air mixture outlets 31 a and a second portion thatserve as the compressed air outlets 31 b. The upstream support 34 andthe downstream support 30 are preferably attached to a circumferentialhousing 37 in a conventional manner. The circumferential housing 37preferably includes an outer housing 37 a and an inner housing 37 b. Theouter housing 37 a and the inner housing 37 b define the fuel-airmixture inlets 29 and the pre-catalyst mixing regions 25 in which thefuel and the first portion of the compressed air mix to form the richfuel-air mixture. Although the mixing of fuel with the first portion ofcompressed air is illustrated as occurring within the catalytic reformerhousing 33, it should be appreciated that the mixing of the fuel withthe compressed air can occur at any point upstream from the catalyticreformer 16.

The catalytic reformer 16 includes means 48 for securing the pluralityof tubes 36 extending between the upstream support 34 and the downstreamsupport 30. Although the tubes 36 are illustrated as cylindrical, itshould be appreciated that the tubes 36 could be of various shapes. Afirst end 46 of the plurality of tubes 36 is attached in fluidcommunication with the compressed air flow inlets 21 defined by theupstream support 34, and a second end 47 of the plurality of tubes 36 isattached in fluid communication with the compressed air outlets 31 bdefined by the downstream support 30. The plurality of tubes 36 can besecured to the upstream and downstream supports 34 and 30 by variousmethods. However, the ends 46 and 47 of the tubes 36 and the supports 34and 30 are preferably brazed to one another in a conventional manner.

The catalytic reformer 16 includes at least one first flow path, beingthe fuel-air mixture flow paths 39, and a plurality of second flowpaths, being the plurality of compressed air flow paths 35. Each of theflow paths 35 and 39 are illustrated by arrows in FIG. 2. The fuel-airmixture flow paths 39 are defined by a plurality of surfaces 38 thatincludes an outer surface 40 of the plurality of tubes 36. Thecompressed air flow paths 35 are defined by an inner surface 26 of theplurality of tubes 36 extending between the plurality of compressed airflow inlets 21 and the compressed flow outlets 31 b. Thus, the flowpaths 39 are separated from flow paths 35 by walls of the tubes 36within the catalytic reformer 16. Preferably, the third flow path, beingthe pilot flow path 12 (shown in FIG. 1), also separately passes throughthe catalytic reformer 16.

The catalytic reformer 16 includes means 43 for introducing thecompressed air flow into the compressed air flow paths 35. The means 43includes the upstream support 34 that is preferably a relativelynon-porous metal plate that defines the plurality of compressed air flowinlets 21. In the illustrated catalytic reformer 16, the reformerhousing 33 includes a second upstream support 27 that defines aplurality of tube bores 28 that include a diameter greater than adiameter of each tube within the plurality 36. The plurality of tubes 36are received within the plurality of tube bores 28. Thus, an areabetween the outer surface 40 of each tube and an inner surface of thetube bore 28 can serve as a portion of the fuel-air mixture flow paths39. The catalytic reformer 16 includes means 42 for introducing thefuel-air mixture flow into the fuel-air mixture flow paths 39. The means42 includes the circumferential housing 37 that defines the fuel-airmixture inlets 29 and the pre-combustion regions 25. Although thepresent invention is illustrated as including two fuel-air mixtureinlets 29, it should be appreciated that the circumferential housing 37could include any number of fuel-air mixture inlets, including one.

The catalytic reformer 16 includes means 44 for contacting the fuel-airmixture flow with the pre-combustion catalyst 41. The means 44 includesat least one of the plurality of surfaces 38 that define the fuel-airmixture flow paths 39 that fluidly connects the fuel-air mixture inlet29 with the fuel-air mixture outlets 31 a. Although any one of theplurality of surfaces 38 can include a coating of the pre-combustioncatalyst 41, the outer surfaces 40 of the tubes 36 preferably includethe coating of the pre-combustion catalyst 41. Thus, as the fuel-airmixture flows through the fuel-air mixture flow paths 39, the fuel-airmixture can make contact with the pre-combustion catalyst 41. Thoseskilled in the art will appreciate that there are a variety ofpre-combustion catalysts that can be coated on the outer surfaces 40 ofthe tubes 36, including, but not limited to, platinum and palladium.Those skilled in the art will also appreciate that a reaction betweenthe fuel-air mixture and the pre-combustion catalyst 41 can reform thefuel. The reformed fuel is richer in hydrogen, which can ultimatelyresult in lower NO_(x) emissions during combustion.

The catalytic reformer 16 includes means 45 for delivering thecompressed air flow and the fuel-air mixture flow to the mixing chamber32 via the fuel-air mixture outlets 31 a and the compressed air outlets31 b defined by the downstream support 30. The fuel-air mixture outlets31 a preferably include pores defined by a material comprising thedownstream support 30, and the compressed air outlets 31 b preferablyinclude outlets of the plurality of tubes 36. Thus, the fuel-air mixtureflow will preferably pass through the pores to the mixing chamber 32,and the compressed air will preferably pass through the tube outlets tothe mixing chamber 32. Within the mixing chamber 32, the rich fuel-airmixture can mix with the compressed air to create the lean fuel-airmixture that is delivered to the combustor 13.

The downstream support 30 preferably includes a plate, and the plate ispreferably comprised of a powdered metal with a predetermined porosity.Because the downstream plate 30 is preferably made from powdered metal,the plate 30 is rather simple and economical to manufacture. Thoseskilled in the art appreciate that there are various sized powderedmetals that can be used to form the downstream plate 30 with thepredetermined porosity by use of a sintering process known in the art.The size of the powdered metal will be selected based on thepredetermined porosity. The predetermined porosity is the porosityrequired to achieve a desired volumetric flow rate of the fuel-airmixture through the downstream plate 30 to the mixing chamber 30 at aknown pressure differential. The larger the desired volumetric flow ratethrough the downstream plate 30, the greater the porosity of thedownstream plate 30. Thus, by controlling the porosity of the downstreamplate 30, along with the air-split between the compressed air flow paths35 and the fuel-air mixture flow paths 39 prior to entering thecatalytic reformer 16, the amount of fuel-air mixture mixing with thecompressed air, and thus, the amount of fuel, within the lean fuel-airmixture that is delivered to the combustor 13 can be controlled. Thoseskilled in the art will appreciate that it is important to accuratelycontrol the fuel and air percentages of the lean fuel-air mixture thatis combusted in order to limit the NO_(x) and other undesirableemissions, from the gas turbine engine 10.

INDUSTRIAL APPLICABILITY

Referring to FIGS. 1 and 2, the operation of the catalytic reformer 16will be discussed for use within the gas turbine engine 10. However, itshould be appreciated that the apparatus, being the catalytic reformer16, can find application in any combustion device. Further, although thepresent invention is illustrated as including one catalytic reformer 16,it should be appreciated that the present invention contemplates the gasturbine engine 10 including any number of catalytic reformers. Forinstance, there could be any number of combustor assemblies 17, eachincluding a catalytic reformer, positioned circumferentially about thecentral shaft coupling the turbine and the compressor. In addition,although the present invention is discussed for pre-combustion usewithin the gas turbine engine 10, the present invention contemplates usewithin post-combustion treatments, such as after-burners.

In order to assemble the catalytic reformer 16, the compressed air flowpaths 35 and the fuel-air mixture flow paths 39 are formed by attachingthe first end 46 of the plurality of tubes 36 to the upstream plate 34and the second end 47 of the tubes 36 to the downstream plate 30.Preferably, the outer surfaces 40 of the tubes 36 are coated with thepre-combustion catalyst 41 prior to the attachment of the tubes 36 tothe plates 34 and 30. It should be appreciated that the tubes 36 can becoated with the pre-combustion catalyst 41 in any manner known to thoseskilled in the art or can be purchased pre-coated. It should further beappreciated that any one of the plurality of surfaces 38, such as aninner surface of the circumferential housing 37, could also be coatedwith the pre-combustion catalyst rather than, or in addition to, thecoating on the outer surface 40 of the tubes 36.

The upstream plate 34 is manufactured to define the plurality ofcompressed air inlets 21 that can receive the first end 46 of theplurality of tubes 36. The upstream plate 34 is preferably manufacturedfrom a non-porous material, thereby restricting the passing of thecompressed air to the plurality of compressed air inlets 21 defined bythe plate 34. In the illustrated examples, the tubes 36 also extendthrough the tube bores 28 of the second upstream support 27. The tubes36 are inserted into the tube bores 28 such that there exists an areabetween the outer surface 40 of the tubes 36 and the inner surface ofthe tube bores 28 through which the fuel-air mixture can flow. Thedownstream plate 30 is manufactured to define the compressed air outlets31 b that can receive the second end 47 of the tubes 36. The downstreamplate 30 is also manufactured to define the fuel-air mixture outlets 31a. Although the fuel-air mixture outlets 31 a can be formed by variousmeans, such as drilling passages through the downstream plate 30, thefuel-air mixture outlets 31 a are preferably formed by comprising thedownstream plate 30 from a porous material, preferably a powdered metalwith the predetermined porosity. The predetermined porosity is theporosity required to achieve the desired volumetric flow rate of thefuel-air mixture through the downstream plate 30. The desired volumetricflow rate is a function of the predetermined percentage of fuel withinthe lean fuel-air mixture that will result in the least amount of NO_(x)and other undesirable emissions. The desired volumetric flow rate, andthus the predetermined porosity, for a known pressure differentialacross the downstream plate 30 can be determined by any method known inthe art. Although the tubes 36 can be secured to the plates 34 and 30 byvarious methods known in the art, the tubes 36 are preferably secured tothe plates 34 and 30 by brazing the first end 46 of the plurality oftubes 36 to the upstream plate 34 and the second end 47 of the tubes 36to the downstream plate 30.

Preferably, the circumferential housing 37 is attached to the upstreamplate 34, the second upstream plate 27 and the downstream plate 30. Thepresent invention contemplates the circumferential housing 37 beingattached to the plates 34, 27 and 30 by various methods, including, butnot limited to, welding the housing 37 to each plate 34, 27 and 30.Although the circumferential housing 37 defines the fuel-air mixtureinlets 29, the present invention contemplates a reformer housing withouta circumferential housing. For instance, the engine housing could beshaped to house the tubes and end plates.

Thus, in the assembled catalytic reformer 16, each tube within theplurality 36 defines a compressed air flow path 35 extending between oneinlet of the compressed air inlets 21 and one of the compressed airoutlets 31 b. It should be appreciated that the present inventioncontemplates any number of tubes defining compressed air flow paths 35.Further, the plurality of surfaces 38 (outer surface of tubes 36 andinner surface of housing 37) define the fuel-air mixture flow paths 39fluidly connecting the fuel-air mixture inlets 29 with the fuel-airmixture outlets 31 a.

Compressed air will flow to the compressed air flow paths 35 from thecompressor assembly via the compressed air plenum 18 that surrounds thecatalytic reformer 16. The compressed air can pass through the catalyticreformer 16 via the plurality of tubes 36 to cool the tubes 36 from theheat of the reaction between the pre-combustion catalyst 41 and thefuel-air mixture. In addition, compressed air, delivered from thecompressor assembly via the compressed air plenum 18, and fuel, injectedby the fuel injector 22, will enter the reformer via the fuel-airmixture inlets 29 and mix within the pre-combustion mixing area 25. Thefuel-air mixture can separately pass through the catalytic reformer 16on the outsides of the tubes 36, and contact the pre-combustion catalyst41 on the outer surfaces 40 of the tubes 36. The fuel-air mixture andthe compressed air can both pass through the downstream plate 30 via thefuel-air mixture outlets 31 a and the compressed air outlets 31 b,respectively, to the mixing chamber 32. The predetermined porosity ofthe downstream plate 30 will allow the desired volumetric flow rate ofthe fuel-air mixture to pass through the fuel-air mixture outlets 31 a.In the mixing chamber 32, the compressed air and the desired amount offuel-air mixture will mix to form a relatively uniformly mixed leanfuel-air mixture which is appropriate for combustion with reduced levelsof NO_(x) emissions. The lean fuel-air mixture is delivered to thecombustor 13, in which it is combusted. The energy created by thecombustion drives the turbine which is operably coupled to drive thecompressor.

The present invention is advantageous because it provides structuralsupport and containment for the catalytic reformer 16. Because thecatalytic reformer 16 is subjected to a relatively hostile environment,including, but not limited to, vibrations, heat and corrosion, the tubes36 must be adequately supported. The upstream and downstream plates 34and 30 provide structural support to the tubes 36 in order to decreasethe likelihood of tube breakage or failure. However, if a reformercomponent fails due to the hostile environment, the downstream plate 30can contain the broken reformer component within the reformer 16. Forinstance, if one of the tubes 36 were to fail due to vibrations, heatand/or corrosion, the downstream plate 30 would prevent the brokenportion from being delivered downstream to the turbine 17 andpotentially severely damaging the engine 10.

Moreover, the upstream and downstream plates 34 and 30 providestructural support and containment without interfering with the desiredflow paths 35 and 39 of the compressed air and the fuel-air mixturethrough the catalytic reformer 16. The compressed air is exclusivelyintroduced into the plurality of tubes 36; whereas, the fuel-air mixtureis exclusively passed on the outside of the tubes 36. The compressed aircan cool the tubes 36 on which the fuel-air mixture is making contactwith the pre-combustion catalyst 41. Both the compressed air and thefuel-air mixture can flow through the outlets 31 and mix in the mixingchamber 32. Thus, the upstream and downstream plates 34 and 30 allow thefuel-rich mixture to make contact with the pre-combustion catalyst 41while the fuel-lean mixture is delivered to the combustor 13. Thus, thecatalytic reformer 16 can reduce NO_(x) emissions without using anexpensive exhaust clean up system.

In addition, the present invention is advantageous because the fuel toair ratio in the lean mixture delivered to the combustor 13 can beaccurately controlled by controlling the porosity of the downstreamplate 30. Engineers can select the porosity that allows the desiredvolumetric flow rate of the fuel-air mixture to pass to the mixingchamber 32 via the downstream plate 30. The desired volumetric flow rateis based on the predetermined amount of fuel within the lean fuel-airmixture that achieves the greatest reduction in NO_(x) emissions for theparticular internal combustion engine. The predetermined porosity of thedownstream plate 30 will help to assure that only a predetermined amountof fuel-air mixture will mix with the compressed air in the secondmixing chamber 32.

It should be understood that the above description is intended forillustrative purposes only, and is not intended to limit the scope ofthe present invention in any way. Thus, those skilled in the art willappreciate that other aspects, objects, and advantages of the inventioncan be obtained from a study of the drawings, the disclosure and theappended claims.

1. An apparatus comprising: an apparatus housing defining at least onefirst flow inlet, and including an upstream support that defines aplurality of second flow inlets and a downstream support that defines aplurality of outlets including a first portion and a second portion; aplurality of surfaces defining at least one first flow path fluidlyconnecting the at least one first flow inlet to the first portion of theplurality of outlets, and at least one of the plurality of surfacesbeing coated with a pre-combustion catalyst; and a plurality of tubesextending between the plurality of second flow inlets and the secondportion of the plurality of outlets, and defining a plurality of secondflow paths.
 2. The apparatus of claim 1 wherein the apparatus housingincludes a circumferencial housing being attached to the upstreamsupport and the downstream support and defining the at least one firstflow inlet.
 3. The apparatus of claim 1 wherein the plurality ofsurfaces includes an outer surface of the plurality of tubes; and thepre-combustion catalyst being coated on the outer surface of theplurality of tubes.
 4. The apparatus of claim 1 wherein the downstreamsupport includes a plate.
 5. The apparatus of claim 4 wherein thedownstream plate being comprised of powdered metal with a predeterminedporosity.
 6. The apparatus of claim 5 wherein the apparatus housingincludes a circumferencial housing being attached to the upstreamsupport and the downstream plate and defining the at least one firstflow inlet; and the pre-combustion catalyst being coated on an outersurface of the plurality of tubes.
 7. A gas turbine engine comprising:an engine housing; and the apparatus of claim 1 attached to the enginehousing.
 8. An apparatus comprising: means for securing a plurality oftubes extending between an upstream support and a downstream support ofan apparatus housing; means for introducing an air flow outside theplurality of tubes via at least one first flow inlet defined by theapparatus housing; means for introducing a fuel-air mixture flow withinthe plurality of tubes via a plurality of second flow inlets defined bythe upstream support; means for contacting the fuel-air mixture flowwith a pre-combustion catalyst; and means for delivering the air flowand the fuel-air mixture flow to a mixing chamber via a plurality ofoutlets defined by the downstream support.
 9. The apparatus of claim 8wherein the downstream support includes a plate.
 10. The apparatus ofclaim 9 wherein the downstream plate being comprised of powdered metalwith a predetermined porosity.
 11. The apparatus of claim 10 wherein theapparatus housing includes a circumferencial housing attached to theupstream support and the downstream plate, and defining the at least onefirst flow inlet.
 12. The apparatus of claim 11 wherein the plurality ofsurfaces includes an outer surface of the plurality of tubes; and thepre-combustion catalyst being coated on the outer surface of theplurality of tubes.
 13. A gas turbine engine comprising: an enginehousing; and the apparatus of claim 8 attached to the engine housing.14. A method of assembling an apparatus comprising the steps of: formingat least one first flow path and a plurality of second flow pathsthrough an apparatus housing, at least in part, by attaching a first endof a plurality of tubes to a plurality of second flow inlets defined byan upstream support and a second end of the plurality of tubes to aportion of a plurality of second flow outlets defined by a downstreamsupport; and coating at least one surface of the first flow path with apre-combustion catalyst.
 15. The method of claim 14 wherein the methodof forming includes a step of manufacturing at least the downstreamsupport from powdered metal with a predetermined porosity.
 16. Themethod of claim 14 wherein the step of forming includes a step ofbrazing the first end and the second end of the plurality of tubes tothe upstream support and the downstream support, respectively.
 17. Themethod of claim 14 wherein the step of forming includes a step ofattaching a circumferencial housing to the upstream support and thedownstream support.
 18. The method of claim 14 wherein the step ofcoating includes a step of coating an outer surface of the plurality oftubes with the pre-combustion catalyst.